Creation of a dual-porosity micromodel for pore-level visualization of multiphase flow

This paper describes the creation and testing of an etched-silicon micromodel that has the features and characteristics of a dual-porosity pore system mimicking those found in certain carbonate reservoir rocks. This micromodel consists of a two-dimensional (2D) pore network etched into a silicon wafer with a bonded glass cover that permits direct visual examination of pore-level displacement mechanisms and pore-network characteristics during fluid flow experiments. The approach began by creating a mosaic of images from a carbonate thin section of a sample with both high porosity and permeability using a scanning electron microscope (SEM) in back-scattered mode (BSE). Connections based on high-pressure mercury injection data were made to ensure that the 2D connectivity in the imaged pore structure was representative of the three dimensional (3D) pore network of the carbonate sample. Microelectronic photolithography techniques were then adapted to create micromodels for subsequent fluid flow experiments. Micromodel surfaces were made oil- or water-wet by various techniques. One of the main advantages of having a representative carbonate dual-porosity micromodel is the ability to observe pore-level mechanisms of multiphase flow and interpret petrophysical properties. Another advantage is that multiple replicates are available with identical conditions for each new experiment. Micromodel utility is demonstrated here through the measurement of porosity, permeability, fluid desaturation patterns, and recovery factors.